From: Omar Sandoval <[email protected]> There are 4 main cases:
1. Inline extents: we copy the data straight out of the extent buffer. 2. Hole/preallocated extents: we indicate the size of the extent starting from the read position; we don't need to copy zeroes. 3. Regular, uncompressed extents: we read the sectors we need directly from disk. 4. Regular, compressed extents: we read the entire compressed extent from disk and indicate what subset of the decompressed extent is in the file. This initial implementation simplifies a few things that can be improved in the future: - We hold the inode lock during the operation. - Cases 1, 3, and 4 allocate temporary memory to read into before copying out to userspace. - Cases 3 and 4 do not implement repair yet. Signed-off-by: Omar Sandoval <[email protected]> --- fs/btrfs/ctree.h | 2 + fs/btrfs/file.c | 12 +- fs/btrfs/inode.c | 462 +++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 475 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 71552b2ca340..3b2aa1c7218c 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -2906,6 +2906,8 @@ int btrfs_run_delalloc_range(struct inode *inode, struct page *locked_page, int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end); void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start, u64 end, int uptodate); +ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter); + extern const struct dentry_operations btrfs_dentry_operations; /* ioctl.c */ diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 27e5b269e729..51740cee39fc 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -390,6 +390,16 @@ int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info) return 0; } +static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) +{ + if (iocb->ki_flags & IOCB_ENCODED) { + if (iocb->ki_flags & IOCB_NOWAIT) + return -EOPNOTSUPP; + return btrfs_encoded_read(iocb, iter); + } + return generic_file_read_iter(iocb, iter); +} + /* simple helper to fault in pages and copy. This should go away * and be replaced with calls into generic code. */ @@ -3457,7 +3467,7 @@ static int btrfs_file_open(struct inode *inode, struct file *filp) const struct file_operations btrfs_file_operations = { .llseek = btrfs_file_llseek, - .read_iter = generic_file_read_iter, + .read_iter = btrfs_file_read_iter, .splice_read = generic_file_splice_read, .write_iter = btrfs_file_write_iter, .mmap = btrfs_file_mmap, diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 8bce46122ef7..174d0738d2c9 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -10593,6 +10593,468 @@ void btrfs_set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end) } } +static int encoded_iov_compression_from_btrfs(struct encoded_iov *encoded, + unsigned int compress_type) +{ + switch (compress_type) { + case BTRFS_COMPRESS_NONE: + encoded->compression = ENCODED_IOV_COMPRESSION_NONE; + break; + case BTRFS_COMPRESS_ZLIB: + encoded->compression = ENCODED_IOV_COMPRESSION_ZLIB; + break; + case BTRFS_COMPRESS_LZO: + encoded->compression = ENCODED_IOV_COMPRESSION_LZO; + break; + case BTRFS_COMPRESS_ZSTD: + encoded->compression = ENCODED_IOV_COMPRESSION_ZSTD; + break; + default: + return -EIO; + } + return 0; +} + +static ssize_t btrfs_encoded_read_inline(struct kiocb *iocb, + struct iov_iter *iter, u64 start, + u64 lockend, + struct extent_state **cached_state, + u64 extent_start, size_t count, + struct encoded_iov *encoded, + bool *unlocked) +{ + struct inode *inode = file_inode(iocb->ki_filp); + struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; + struct btrfs_path *path; + struct extent_buffer *leaf; + struct btrfs_file_extent_item *item; + u64 ram_bytes; + unsigned long ptr; + void *tmp; + ssize_t ret; + + path = btrfs_alloc_path(); + if (!path) { + ret = -ENOMEM; + goto out; + } + ret = btrfs_lookup_file_extent(NULL, BTRFS_I(inode)->root, path, + btrfs_ino(BTRFS_I(inode)), extent_start, + 0); + if (ret) { + if (ret > 0) { + /* The extent item disappeared? */ + ret = -EIO; + } + goto out; + } + leaf = path->nodes[0]; + item = btrfs_item_ptr(leaf, path->slots[0], + struct btrfs_file_extent_item); + + ram_bytes = btrfs_file_extent_ram_bytes(leaf, item); + ptr = btrfs_file_extent_inline_start(item); + + encoded->len = (min_t(u64, extent_start + ram_bytes, inode->i_size) - + iocb->ki_pos); + ret = encoded_iov_compression_from_btrfs(encoded, + btrfs_file_extent_compression(leaf, item)); + if (ret) + goto out; + if (encoded->compression) { + size_t inline_size; + + inline_size = btrfs_file_extent_inline_item_len(leaf, + btrfs_item_nr(path->slots[0])); + if (inline_size > count) { + ret = -EFBIG; + goto out; + } + count = inline_size; + encoded->unencoded_len = ram_bytes; + encoded->unencoded_offset = iocb->ki_pos - extent_start; + } else { + encoded->len = encoded->unencoded_len = count = + min_t(u64, count, encoded->len); + ptr += iocb->ki_pos - extent_start; + } + + tmp = kmalloc(count, GFP_NOFS); + if (!tmp) { + ret = -ENOMEM; + goto out; + } + read_extent_buffer(leaf, tmp, ptr, count); + btrfs_free_path(path); + path = NULL; + unlock_extent_cached(io_tree, start, lockend, cached_state); + inode_unlock(inode); + *unlocked = true; + if (copy_to_iter(encoded, sizeof(*encoded), iter) == sizeof(*encoded) && + copy_to_iter(tmp, count, iter) == count) + ret = count; + else + ret = -EFAULT; + kfree(tmp); + +out: + btrfs_free_path(path); + return ret; +} + +struct btrfs_encoded_read_private { + struct inode *inode; + wait_queue_head_t wait; + atomic_t pending; + bool uptodate; + bool skip_csum; +}; + +static bool btrfs_encoded_read_check_csums(struct btrfs_io_bio *io_bio) +{ + struct btrfs_encoded_read_private *priv = io_bio->bio.bi_private; + struct inode *inode = priv->inode; + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); + u32 sectorsize = fs_info->sectorsize; + struct bio_vec *bvec; + struct bvec_iter_all iter_all; + u64 offset = 0; + + if (priv->skip_csum) + return true; + bio_for_each_segment_all(bvec, &io_bio->bio, iter_all) { + unsigned int i, nr_sectors, pgoff; + + nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec->bv_len); + pgoff = bvec->bv_offset; + for (i = 0; i < nr_sectors; i++) { + int csum_pos; + + csum_pos = BTRFS_BYTES_TO_BLKS(fs_info, offset); + if (__readpage_endio_check(inode, io_bio, csum_pos, + bvec->bv_page, pgoff, + io_bio->logical + offset, + sectorsize)) + return false; + offset += sectorsize; + pgoff += sectorsize; + } + } + return true; +} + +static void btrfs_encoded_read_endio(struct bio *bio) +{ + struct btrfs_encoded_read_private *priv = bio->bi_private; + struct btrfs_io_bio *io_bio = btrfs_io_bio(bio); + + if (bio->bi_status || !btrfs_encoded_read_check_csums(io_bio)) + priv->uptodate = false; + if (!atomic_dec_return(&priv->pending)) + wake_up(&priv->wait); + btrfs_io_bio_free_csum(io_bio); + bio_put(bio); +} + +static bool btrfs_submit_encoded_read(struct bio *bio) +{ + struct btrfs_encoded_read_private *priv = bio->bi_private; + struct inode *inode = priv->inode; + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); + blk_status_t status; + + atomic_inc(&priv->pending); + + if (!priv->skip_csum) { + status = btrfs_lookup_bio_sums_at_offset(inode, bio, + btrfs_io_bio(bio)->logical, + NULL); + if (status) + goto out; + } + + status = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA); + if (status) + goto out; + + status = btrfs_map_bio(fs_info, bio, 0, 0); +out: + if (status) { + bio->bi_status = status; + bio_endio(bio); + return false; + } + return true; +} + +static ssize_t btrfs_encoded_read_regular(struct kiocb *iocb, + struct iov_iter *iter, + u64 start, u64 lockend, + struct extent_state **cached_state, + struct block_device *bdev, + u64 offset, u64 disk_io_size, + size_t count, + const struct encoded_iov *encoded, + bool *unlocked) +{ + struct inode *inode = file_inode(iocb->ki_filp); + struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; + struct btrfs_encoded_read_private priv = { + .inode = inode, + .wait = __WAIT_QUEUE_HEAD_INITIALIZER(priv.wait), + .pending = ATOMIC_INIT(1), + .uptodate = true, + .skip_csum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM, + }; + struct page **pages; + unsigned long nr_pages, i; + struct bio *bio = NULL; + u64 cur; + size_t page_offset; + ssize_t ret; + + nr_pages = (disk_io_size + PAGE_SIZE - 1) >> PAGE_SHIFT; + pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS); + if (!pages) + return -ENOMEM; + for (i = 0; i < nr_pages; i++) { + pages[i] = alloc_page(GFP_NOFS | __GFP_HIGHMEM); + if (!pages[i]) { + ret = -ENOMEM; + goto out; + } + } + + i = 0; + cur = 0; + while (cur < disk_io_size) { + size_t bytes = min_t(u64, disk_io_size - cur, + PAGE_SIZE); + + if (!bio) { + bio = btrfs_bio_alloc(offset + cur); + bio_set_dev(bio, bdev); + bio->bi_end_io = btrfs_encoded_read_endio; + bio->bi_private = &priv; + bio->bi_opf = REQ_OP_READ; + btrfs_io_bio(bio)->logical = start + cur; + } + + if (bio_add_page(bio, pages[i], bytes, 0) < bytes) { + bool success; + + success = btrfs_submit_encoded_read(bio); + bio = NULL; + if (!success) + break; + continue; + } + i++; + cur += bytes; + } + + if (bio) + btrfs_submit_encoded_read(bio); + if (atomic_dec_return(&priv.pending)) + wait_event(priv.wait, !atomic_read(&priv.pending)); + if (!priv.uptodate) { + ret = -EIO; + goto out; + } + + unlock_extent_cached(io_tree, start, lockend, cached_state); + inode_unlock(inode); + *unlocked = true; + + if (copy_to_iter(encoded, sizeof(*encoded), iter) != sizeof(*encoded)) { + ret = -EFAULT; + goto out; + } + if (encoded->compression) { + i = 0; + page_offset = 0; + } else { + i = (iocb->ki_pos - start) >> PAGE_SHIFT; + page_offset = (iocb->ki_pos - start) & (PAGE_SIZE - 1); + } + cur = 0; + while (cur < count) { + size_t bytes = min_t(size_t, count - cur, + PAGE_SIZE - page_offset); + + if (copy_page_to_iter(pages[i], page_offset, bytes, + iter) != bytes) { + ret = -EFAULT; + goto out; + } + i++; + cur += bytes; + page_offset = 0; + } + ret = count; +out: + for (i = 0; i < nr_pages; i++) { + if (pages[i]) + put_page(pages[i]); + } + kfree(pages); + return ret; +} + +ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter) +{ + struct inode *inode = file_inode(iocb->ki_filp); + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); + struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; + ssize_t ret; + size_t count; + struct block_device *em_bdev; + u64 start, lockend, offset, disk_io_size; + struct extent_state *cached_state = NULL; + struct extent_map *em; + struct encoded_iov encoded = {}; + bool unlocked = false; + + ret = check_encoded_read(iocb, iter); + if (ret < 0) + return ret; + if (ret == 0) { +empty: + if (copy_to_iter(&encoded, sizeof(encoded), iter) == + sizeof(encoded)) + return 0; + else + return -EFAULT; + } + count = ret; + + file_accessed(iocb->ki_filp); + + inode_lock(inode); + + if (iocb->ki_pos >= inode->i_size) { + inode_unlock(inode); + goto empty; + } + start = ALIGN_DOWN(iocb->ki_pos, fs_info->sectorsize); + /* + * We don't know how long the extent containing iocb->ki_pos is, but if + * it's compressed we know that it won't be longer than this. + */ + lockend = start + BTRFS_MAX_UNCOMPRESSED - 1; + + for (;;) { + struct btrfs_ordered_extent *ordered; + + ret = btrfs_wait_ordered_range(inode, start, + lockend - start + 1); + if (ret) + goto out_unlock_inode; + lock_extent_bits(io_tree, start, lockend, &cached_state); + ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), start, + lockend - start + 1); + if (!ordered) + break; + btrfs_put_ordered_extent(ordered); + unlock_extent_cached(io_tree, start, lockend, &cached_state); + cond_resched(); + } + + em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, + lockend - start + 1, 0); + if (IS_ERR(em)) { + ret = PTR_ERR(em); + goto out_unlock_extent; + } + em_bdev = em->bdev; + + if (em->block_start == EXTENT_MAP_INLINE) { + u64 extent_start = em->start; + + /* + * For inline extents we get everything we need out of the + * extent item. + */ + free_extent_map(em); + em = NULL; + ret = btrfs_encoded_read_inline(iocb, iter, start, lockend, + &cached_state, extent_start, + count, &encoded, &unlocked); + goto out; + } + + /* + * We only want to return up to EOF even if the extent extends beyond + * that. + */ + encoded.len = (min_t(u64, extent_map_end(em), inode->i_size) - + iocb->ki_pos); + if (em->block_start == EXTENT_MAP_HOLE || + test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) { + offset = EXTENT_MAP_HOLE; + } else if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) { + offset = em->block_start; + /* + * Bail if the buffer isn't large enough to return the whole + * compressed extent. + */ + if (em->block_len > count) { + ret = -EFBIG; + goto out_em; + } + disk_io_size = count = em->block_len; + encoded.unencoded_len = em->ram_bytes; + encoded.unencoded_offset = iocb->ki_pos - em->orig_start; + ret = encoded_iov_compression_from_btrfs(&encoded, + em->compress_type); + if (ret) + goto out_em; + } else { + offset = em->block_start + (start - em->start); + if (encoded.len > count) + encoded.len = count; + /* + * Don't read beyond what we locked. This also limits the page + * allocations that we'll do. + */ + disk_io_size = min(lockend + 1, iocb->ki_pos + encoded.len) - start; + encoded.len = encoded.unencoded_len = count = + start + disk_io_size - iocb->ki_pos; + disk_io_size = ALIGN(disk_io_size, fs_info->sectorsize); + } + free_extent_map(em); + em = NULL; + + if (offset == EXTENT_MAP_HOLE) { + unlock_extent_cached(io_tree, start, lockend, &cached_state); + inode_unlock(inode); + unlocked = true; + if (copy_to_iter(&encoded, sizeof(encoded), iter) == + sizeof(encoded)) + ret = 0; + else + ret = -EFAULT; + } else { + ret = btrfs_encoded_read_regular(iocb, iter, start, lockend, + &cached_state, em_bdev, offset, + disk_io_size, count, &encoded, + &unlocked); + } + +out: + if (ret >= 0) + iocb->ki_pos += encoded.len; +out_em: + free_extent_map(em); +out_unlock_extent: + if (!unlocked) + unlock_extent_cached(io_tree, start, lockend, &cached_state); +out_unlock_inode: + if (!unlocked) + inode_unlock(inode); + return ret; +} + #ifdef CONFIG_SWAP /* * Add an entry indicating a block group or device which is pinned by a -- 2.23.0
